Glycoprotein hormone alpha-subunit secretion in patients with pituitary adenomas: influence of TRH, LRH and bromocriptine.
Twelve patients with pituitary adenomas and increased serum concentration of the glycoprotein hormone alpha-subunit were studied. Eight patients were acromegalic and one had a FSH producing tumour. The adenomas in 9 patients had undergone subtotal operative removal and/or external irradiation but no patient was studied within 3 months of these treatments. Many of the acromegalic patients, with moderately elevated alpha-levels, showed marked increases in alpha-concentration after TRH and/or LRH, compared with controls. The non-acromegalic patients, with the highest alpha-levels, showed poor responses to releasing hormones. These results suggest that excessive alpha-subunit secretion in acromegalic patients is often under hypothalamic control whereas in non-acromegalic patients it is often autonomous. Seven patients, 4 with acromegaly, were then given oral bromocriptine, 5 mg over 3 h. There was a significant fall in log mean alpha-level at 4 and 5 h (P less than 0.02). Six patients took bromocriptine for 1--2 months. Log mean alpha-concentration was significantly reduced at the end of treatment (P less than 0.02) and then recovered to basal levels after stopping treatment for one week. alpha-Subunit hypersecretion in some patients with pituitary adenomas is therefore modulated by dopaminergic control mechanisms.
D000172:Acromegaly / Q000150:complications / Q000188:drug therapy / Q000503:physiopathology; D000236:Adenoma / Q000150:complications / Q000378:metabolism*; D001971:Bromocriptine / Q000627:therapeutic use*; D005260:Female; D006023:Glycoproteins / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D006801:Humans; D008297:Male; D010911:Pituitary Neoplasms / Q000150:complications / Q000378:metabolism*; D011954:Receptors, Dopamine / Q000187:drug effects; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*
D006023:Glycoproteins; D011954:Receptors, Dopamine; D007987:Gonadotropin-Releasing Hormone; D001971:Bromocriptine; D013973:Thyrotropin-Releasing Hormone